Hydroisomerization processes and catalysts therefor are well known, catalysts including noble metals, Pt, Pd, Rh supported on flourided alumina, and Group VIII non-noble metals with or without one or more Group VI metals supported on silica, alumina or silica-alumina. These catalysts are usually bifunctional; they contain a metal hydrogenation catalyst and an acidic cracking function.
Carbon oxides, carbon dioxide and particularly carbon monoxide have have been disclosed in U.S. Pat. No. 3,711,399 as inhibitors of hydrocracking in isomerization processes using highly acidic fluorine containing catalyst, the carbon oxide being added in relatively small amounts. Hydrocracking is virtually completely suppressed and C.sub.4 - yields are virtually negligible.
Nevertheless, LPG and light liquids yields in these processes are desirable to insure appropriate pour points for diesel and jet fuels. Methane, by itself, is the particularly undesirable product since, for example, isomerized products can be made from Fischer-Tropsch waxes which, in turn, ultimately come from methane via synthesis gas production. Consequently, a desire exists for isomerization processes that suppress or substantially eliminate methane formation without substantial affect on LPG and light liquid yields.